1. Field of the Invention
The invention relates to apparatus and methods for obtaining blood samples. More particularly, the present invention is directed to apparatus and methods for obtaining both arterial blood gas and clinical laboratory samples from a single hypodermic needle puncture of a patient.
2. Technology Review
Blood samples are routinely obtained in virtually all areas of medical health care. Analysis of a person's blood provides a significant amount of information regarding the person's overall state of health. Blood for clinical laboratory analysis is most often obtained by venipuncture (puncture of a vein). Puncturing a vein to obtain blood for clinical laboratory analysis is preferred in most cases because veins are generally close to the skin's surface, transport large quantities of blood, and the blood flows in the vein at a lower pressure than in the arteries.
In specific instances, however, venous blood samples do not provide the information desired. Many times it is necessary to know the arterial blood gas concentration and pH of the arterial blood in order to correctly diagnose and treat certain diseases and conditions. Arterial blood gas (sometimes referred to as "ABG") analysis provides a measurement of the partial pressure of oxygen and of carbon dioxide in arterial blood, as well as the pH of the blood. The partial pressure of oxygen, together with hemoglobin (hemoglobin is also derived from an ABG), is a measurement of the amount of oxygen in arterial blood. Arterial blood gas analysis provides means for assessing the adequacy of oxygenation and ventilation of the blood. This provides a direct indication of lung function in supplying oxygen to the body and in removing carbon dioxide. Arterial blood gas analysis also provides information regarding the acid-base balance in the body and whether acidosis or alkalosis is present and if so to what degree.
Obtaining a sample of arterial blood for blood gas analysis is generally much more difficult than obtaining a sample of blood from a vein. Arteries are generally located deeper within the patient making them more difficult to locate and requiring a deeper hypodermic puncture. Arteries also operate under significantly higher pressure than veins, increasing the risk of hemorrhage after puncturing the artery. Perhaps the most significant procedural difference in obtaining arterial samples as opposed to venous samples is that the arterial blood samples are preferably not exposed to air. Any air bubbles in the arterial blood sample may affect the ultimate measurement of the partial pressure of oxygen within the blood.
Increasingly the blood gas technician is being asked to collect not only a sample for blood gas analysis, but also a sample for standard clinical laboratory analysis. Normally the two blood samples are obtained by independently puncturing a vein to obtain the clinical laboratory blood sample and puncturing an artery to obtain the arterial blood gas sample. This technique, however, requires two separate needle punctures to obtain the two blood samples. This technique increases the time and difficulty in obtaining the necessary samples.
In some situations it may be difficult or inconvenient for the technician to obtain blood from a vein, yet both a clinical laboratory sample and an arterial blood gas sample are needed. Such cases may arise, for example, in a code blue emergency situation (cardiac arrest) or where a suitable vein cannot be located on the patient. In these cases, one technique for obtaining both clinical laboratory blood samples and arterial blood gas samples is by taking a blood gas syringe with a three-way valve stop-cock placed between the blood gas syringe tip and the hypodermic needle. The clinical laboratory blood sample syringe is attached to the three-way valve at a right angle to the blood gas syringe. Using this apparatus, the three-way valve is positioned such that the blood gas syringe fills. Then the valve is turned, while the needle is still placed within the artery, such that the laboratory sample syringe is filled. This apparatus permits both blood samples to be obtained from a single arterial puncture.
This technique, however, requires two technicians. The first technician punctures the artery and obtains the arterial blood gas sample. Once the blood gas sample is obtained, the second technician must turn the three-way valve to direct the blood flow into the clinical laboratory syringe and the pull on the clinical laboratory syringe plunger to fill the syringe with blood. This "pulling" is at a 90.degree. angle from the blood gas syringe while the needle is within the artery. The first technician must hold the hypodermic needle within the artery steady while the second technician draws the clinical laboratory blood sample.
This procedure is both inefficient and awkward for the technicians. Moreover, the method poses the clear danger of trauma to the artery. It is generally recognized that when manual withdrawal of the blood gas syringe piston is required, traumatization of the artery may result. The risk of trauma is particularly severe where the clinical laboratory piston is pulled at a 90.degree. angle relative to the needle within the artery. There is a significant risk that the sharp tip of the hypodermic needle could sever or damage the artery resulting in serious hemorrhage.
An arterial line catheter is often inserted into patients from whom frequent arterial blood samples are required. The arterial line catheter is kept free of blood clots by the pressurized flow of an anticoagulant, such as sodium heparin, through the catheter. In order to obtain an arterial blood sample from an arterial line, a stop-cock in the arterial line catheter is adjusted to stop the anticoagulant flow and permit the arterial blood to fill the line. The desired samples are then taken. For each sample, the arterial line is momentarily open and exposed to the atmosphere. Thus, where both a clinical laboratory sample and blood gas sample are requested, the arterial line is open at least three times: first, to connect an arterial blood gas syringe; second, to remove the arterial blood gas syringe and connect the clinical laboratory syringe; and third, to remove the clinical laboratory syringe. Each time the arterial line is open, there is a risk of introducing infection into the patient.
From the foregoing, it will be appreciated that what is needed in the art are apparatus and methods for obtaining clinical laboratory and arterial blood gas samples which require only a single hypodermic needle puncture. It would be a significant advancement in the art to provide apparatus and methods for obtaining clinical laboratory and arterial blood gas samples which reduce the risk of arterial trauma to the patient.
It would be a further advancement in the art to provide apparatus and methods for obtaining clinical laboratory and arterial blood gas samples in which only one technician is required to obtain both samples. It would be yet another important advancement in the art to provide apparatus and methods for obtaining clinical laboratory and arterial blood gas samples which reduce the risk of infection to the patient.
Such methods and apparatus are disclosed and claimed herein.